Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

BIOLOGY · Stage 7 · Chapter 1: Classification and Life

Biology 1.3 Classification and species

5 min read 5 parts Lesson 3 of 11

0%read
Lesson summary

Biology 1.3 Classification and species — Alhussan International Academy — Biology (Stages 7–9) notes: Explain why organisms are classified, define a species, and use two-part scientific names.Classification = sorting organisms into groups using their similarities and differences.…

  • Importance
  • Big groups first
  • Smaller groups
  • Living organisms
  • Different species
  • Identified species

Section 1 of 5Why classify

  • Classification = sorting organisms into groups using their similarities and differences.
    • Features can be easy to see, such as the number of legs or type of flower, or harder to see, such as root length or whether an animal has a backbone.
  • Importance
    • it shows how many different types of living organisms there are, makes them easy to identify and compare,
      • and helps scientists worldwide know which organisms are discussed.
  • History
    • Carl Linnaeus sorted organisms by physical features in the 1700s, and modern scientists also compare DNA.

Section 2 of 5Classifying organisms into groups

  • Big groups first
    • is it a plant or an animal?
    • Plants make their own food, but animals eat other living things.
  • Smaller groups
    • this level is helpful but does not identify particular organisms, since birds all have feathers but include an ostrich and a hummingbird.
  • Living organisms
    • a basic classification covers animals, plants, fungi and other groups, and asks about viruses.
  • Levels
    • kingdom, phylum, class, order, family, genus and species, from largest to smallest.
    • Organisms in each smaller group have more features in common, and members of one species are the most closely related.

Section 3 of 5What is a species

  • Species = a group of organisms that can reproduce to produce fertile offspring (offspring that can themselves reproduce).
  • Different species
    • they cannot usually breed with each other.
  • Hybrids
    • when different species do breed, the offspring are hybrids, which are usually infertile.
    • A mule, the strong, intelligent offspring of a female horse and male donkey, cannot breed,
      • so horses and donkeys are separate species and mules are not a species.
  • Limits
    • asexual organisms and fossils cannot be tested by breeding, and some species form fertile hybrids, so structure, behaviour and DNA are also used.

Section 4 of 5Number of species

  • Identified species
    • about 2 million species have been identified.
  • Estimates
    • biologists think there may be as many as 5 million species on Earth.
  • Why new species are hard to find
    • they may be very small or rare, live in unexplored places such as the deep ocean, or live in areas with many species such as rainforests.

Section 5 of 5Naming species

  • Local names
    • they vary and cause confusion, such as the clouded leopard, called the tree tiger in Borneo and the mint leopard in southern China.
  • Scientific name
    • each species has a two-part name, and similar species share the first part.
    • Lions are Panthera leo, tigers Panthera tigris, horses Equus caballus and donkeys Equus asinus.
    • Humans are Homo sapiens.
  • Rules
    • the first part is the genus, with a capital letter, and the second is the species, in lower case, both in italics or underlined.
  • Importance
    • it tells scientists around the world exactly which organism is meant.

Last updated: